Implantable medical devices, such as a stents, grafts, stent-grafts, vena cava filters and the like, and delivery assemblies are utilized in a number of medical procedures and situations, and as such their structure and function are well known.
Self-expanding, inflation expandable and hybrid stents are available in a variety of designs and configurations. Examples are disclosed in U.S. Pat. No. 6,348,065, U.S. 2002-0055770-A1 and U.S. Pat. No. 6,168,621, incorporated herein by reference.
Stents are generally tubular but have been embodied in many different configurations and have been made of many materials, including metals and plastic. Ordinary metals such as stainless steel have been used, as have shape memory metals such as Nitinol and the like. Stents may also be made of bio-absorbable plastic materials. Stents may be formed from wire, flat sheets, tube stock, and the like.
A number of techniques have been suggested for the fabrication of stents from sheets and tubes. One such technique involves laser cutting a pattern into a sheet of material and rolling the sheet into a tube, or directly laser cutting the desired pattern into a tube. Other techniques involve cutting a desired pattern into a sheet or a tube via chemical etching or electrical discharge machining.
Laser cutting of stents has been described in a number of publications including U.S. Pat. No. 5,780,807 to Saunders, U.S. Pat. No. 5,922,005 to Richter and U.S. Pat. No. 5,906,759 to Richter, the disclosures of which are incorporated herein by reference. Other references wherein laser cutting of stents is described include: U.S. Pat. No. 5,514,154, U.S. Pat. No. 5,759,192, U.S. Pat. No. 6,131,266 and U.S. Pat. No. 6,197,048, the disclosures of which are incorporated herein by reference.
A typical laser cutting system relies on a laser to produce a beam which is conditioned as necessary via an optical unit and focused into a spot beam which is impinged against a hollow tube that is to become the stent. The hollow tube may be moved via a rotational motor drive and linear motion drive.
An example of a conventional laser for cutting a stent is a highly focused pulsed Nd:YAG laser which has a pulse duration in the range of approximately 0.1 to 20 milliseconds. This is a long pulse time for cutting and characteristically produces a relatively large melt zone and heat affected zone (HAZ) on the metal. The conventional laser cutting process typically results in the formation of melt dross on the inside edge of the cut tube or sheet. This dross must be cleaned off in subsequent processes.
Cutting and processing systems have been developed that incorporate a water column and laser. SYNOVA Inc., of Lausanne, Switzerland, provides a laser-microjet that uses a laser beam that is contained within a water jet similar in principle to an optical fiber transmission.
The SYNOVA laser-microjet relies on a low pressure water column to contain the laser, to act as a cooling mechanism and to remove cutting debris.
The use of a hybrid liquid-jet/laser system such as the SYNOVA system to cut a stent presents new manufacturing concerns. Procedures which produce a satisfactory end product when using a conventional laser system are not generally applicable when using a hybrid liquid-jet/laser system. Thus, new procedures must be developed.
All U.S. patents and applications and all other published documents mentioned anywhere in this application are incorporated herein by reference in their entirety.
A brief summary of some of the claimed embodiments is set forth below. Additional details of the summarized embodiments and/or additional embodiments may be found in the Detailed Description below.
A brief abstract of the technical disclosure in the specification is provided as well only for the purposes of complying with 37 C.F.R. 1.72. The abstract is not intended to be used for interpreting the scope of the claims.